The present disclosure is related to the field of chemical sensing. More specifically, the present disclosure is related to a paper-based microfluidic calorimetric chemical sensor.
Common paper-based chemical sensors use a paper strip to absorb a fluid that is to be tested for the presence of a substance. Paper strip chemical sensors often use colormetric detection, wherein some or all of the paper strip changes color when exposed to liquid having the chemical to be tested for. One such accommodating sample is a pregnancy test wherein at least a portion of the testing strip changes color in the presence of the hormone HCG. Colormetric sensors are generally limited to qualitative detections of the presence of a chemical substance. Colormetric sensors have limited, if any, ability to convey quantitative measures. Such quantitative results are reported by various color changes that are associated with bands or bins of concentration values.
Another form of paper-based chemical sensor is an electrochemical sensor whereby a chemical reaction/interaction with the substance to be measured yields a conductive by-product resulting in a variable electrical response when energization is applied to the by-product. One example of these such systems is a blood glucose meter. While the electrochemical detection enables a quantitative measurement of the concentration or amount of the substance to be measured, recent studies have shown that these quantitative determinations can have a large error. Furthermore, electrochemical detection requires a chemical reaction that yields conductive by-products. This specialized reaction by-product limits the substances that may be sensed with these types of paper-based chemical sensors.
Thermal detection methods have been previously used to explore chemical interactions. However, currently available macro-scale calorimeter solutions are impractical for use in disposable and inexpensive sensing applications.